Mortar tube with plug type base cap



June 20, 1950 s. wElss MORTAR TUBE WITH PLUG TYPE BASE CAP Filed Dec. 3, 1946 W .m m\ m s m m S JM nu Q .t M Nm. TN. \N QN/Uw w. Q w d Q \m.n @MRM mm QN Nm., M -5PM -dimm NT ww Q N v ummm um@ S Patented June 20, 1950 MORTAR TUBE WITH PLUGTYPE BASE CAP Saul Weiss, WashingtornD. C. Application December 3, 1946, Serial No. 713,725l

(Granted under the act of March 3,v 1883, as amended April 30, 1928; 370 '0. G. 757) 3 Claims.

The inventionrdescribed in the following specification and claims may be manufactured and used'by or for the vGovernment for governmental purposes without the payment to me of any royalty thereon. y

This invention relates to improvements in artillery and more particularly in trench and field mortars of the typeadapted to be assembled, disassembled, manually transported and reassembled in the shortest possible time.

`It has long been recognized Eby those skilled in the design and production of mortars, that they must be made of the lightest possible construction capable of withstanding the concussion and shocks incidental to employment in battle. Consequently this art is crowded and it is now exceedingly difficult to reduce by a single ounce the weight of a modern mortar without increasing the hazard of it exploding in action. Despite this situation, it is a major purpose of the present invention to provide a mortar of lighter -but equally dependable construction.

Another object is the provision of a mortar having self-sealing means whereby the gas pressure and the heat energy generated during the firing of the mortar may be utilized to prevent the escapeof thegases from the rear end portion of the mortar tube.

The additional objects, advantages and novel features of this invention will become apparent as the specification proceeds and from the construction, arrangement and combination of parts illustrated in the accompanying drawings, in which:

Figure 1 yis a, fragmentary, -partly elevational, partly cross-sectional View of a mortar embodying a preferred form of this invention,

Figure 2 is a cross-sectional Yview showing the construction of the mortar cap andadjacent portions, of the'mortar tube. and

Figure 3is an enlargement'of an upper portion of Figure 2.

Referring now to the above-mentioned drawings, the mortar, generally indicated by the numeral I, includes among other elements a mortar tube 2, a base cap 3 and a firing mechanism housing d. The rear portion of the housing terminates in a ball 5 having opposite ats i5 whereby the ball is adapted to be mounted in a socketed plate (not shown) which serves as the base of the mortar.

The upper end of this housing is internally recessed and threaded at 'i to receive an externally threaded adapter 8. This adapter is in turn internally threaded to receive a, bushing 9 in 2,5, formed integrally with each other.

which there `is fslidably mounted a firing pin (not shown) whereby the percussion cap (not shown) of the mortar projectile Ill is detonated when the mortar is fired. The extreme front end of this bushing `is `preferably of suflicient area to completely support the tubularrear end portion II of the projectile and. is provided with a smooth flat surface I2 extending in a plane at right angles to thelongitudinal center line of the tube in order that'the projectile may be mounted flushwith this flat surface and in a more complete alignment with the longitudinal axis of the mortar tube when the-mortar is fired.

Referring again vto lFigure 1, it will also be seen that the front end portion I3 of the bushing extends inwardly into the mortar tube beyond the forward end -portion la of the adapter and is formed polygonallyor nut-shaped to permit the bushing to be tightly screwed in its assembled position on the r adapter with any suitable socket wrench.

The mortar base cap 3 consists of a circular base portion I5 and a circular wall portion IS This base portion has a central threaded open portion Il whereby the cap may be threadedly connected t0 the adapter. The base portion is, for convenience in assembling, preferably provided with diametrically opposed recessed portions I8 which are provided for `the purpose of receiving the pins of a pin wrench (notshown) whereby the cap base may be screwed on the adapter. For purposes which will become more apparent as .y this specification proceeds, the cap wall I6 (see `lar slot 2d. The slot 24 is adapted to snugly receive an annular projection 25 extending rearwardly from the rear edge 26 of the mortar tube. This rear end portion of the tube is machined internally to Aprovide a cut-away portion 28, a

` raised threaded portion `29, a, second cut-away portion 3B and an adjacent shoulder 3l.

y In the assembled mortar, the above described arrangement provides an extremely efficient whereby the highly heated gases are prevented from escaping between the mortar tube and the cap. Referring now particularly to Figure 3, it will be seen that the front part 32 of the beveled portion 23 contacts the adjacent inside surface of the mortar tube at 33 while the midportion of the beveled portion is opposite to a cavity 34 provided by the machined down portions in the tube and the cap immediately in rear of the shoulder 3l. When the projectile is being red from the mortar, an exceeding high but momentary hot high gas pressure is, of course, generated in the rear of the projectile and this pressure forces the weakened beveled portion outwardly toward the cavity and that portion of the inside surface of the tube opposite the front part 32 of the internally beveled circumferential por-V, tion of the wall of the cap. Since the air in this cavity cannot effectively oppose this internal pressure, this pressure is transmitted to the front part 32 of the beveled portion where it is added to the force exerted outwardly against the front part 32- and causes that part to press with a substantially greater force against the adjacent inner surface of the tube. This arrangement, therefore, provides a uniquely effective gas pressure-operated seal which prevents the heated gases from escaping outwardly past the beveled portion 23.

Reference is now made (see Figure 3) particularly to the annular projection 25 of the tube in the annular slot of the mortar cap and to the well known fact that, during ring, the rear half portion of a mortar tube :is more .highly heated than the cap portion. Because of Y' this more highly heated condition of theftube, its projection 25 is both pressed downwardly into the slot 25 and outwardly against the adjacent portion of the cap and thereby provides an effective thermally operated seal whereby a second barrier is presented to the high pressure gas seeking to escape between the tube and the cap.

From the foregoing it'will' become apparent that the present inventionprovides both a pres- Asure operated and a thermally operated sealing means whereby the mortar is greatly strengthened where the high pressure gases are most likely to escape from the rear end portion of the mortar tube. It is also apparent that the mortar cap `can safely be made both smaller and lighter because the cap is operatively connected to the inside wall portion of the mortar tube instead of being secured in the conventional manner to the outside of this tube. The connecting of the cap to the inside wall instead of the outside wall also provides the additional advantage that no raised externally threaded portion is required onthe outside wall of the tube for threadedly connecting an internally threadedcap to the tube. The elimination of this necessity for prodiving this raised externally threaded portion on the mortar tube also eliminates the necessity for reducing the outside diameter of the Vrest of the tube as is done in conventional mortar construction.

It will of course be understood that only a preferred form of the present invention is herein disclosed and other modifications may be made within the spirit of this invention and the scope of the appended claims.

I claim:

l. A mortar of the class described, said mortar including a hollow metallic tube, a rear end por-Y tion and a cap, said cap having a circular base portion and a circular longitudinally extending wall portion, said base portion being threadedly secured to said rear end portion, said extending wall portion being threadedly connected by an integral external threaded portion to the inside surface of said t-ube and being spaced apart from said tube at either end of the threaded portion, said wall portion terminating inside of said tube in an internally beveled end portion extending from one end of said threaded portion to the inside surface of said tube and forming a circular soy vinclosecl annular recess between the wall and the cap.

2. A mortar of the class described, said mortar including a hollow metallic tube, a rear end portion and a cap, said `cap having a base portion and a longitudinally extending wall portion, said base portion being threadedly secured to said rear end portion, said wall portion being threadedly connected by an integral external threaded portion to the inside surface of` said tube and being spaced apart from said tube at either endof the threaded portion, said W'all portion terminating inside ofv said tube in an internally beveled end portion ex-y tending from a position parallel to one end of said threaded portion to the interior surface of said tube and forming a weakened section coincident with the portion spaced apart from said tube, said cap having an annular radially projecting shoulder provided with an annular longitudinally and rearwardly extending slottedfportion, said tube having an annular end portion extending into said slotted portion.

3. In a mortar of the cla-ss described, a rear end portion, a cap rigidly secured to said rear end portion and `being provided with an outwardly projecting external threaded portion, and a tube having an inwardly projecting internal threaded portion, said cap and said tube being threadedly connected together by said threaded portions and, forming hollow ring adjacent either end of said`V threaded portions, said cap extending inwardly into said tube and terminatingbeyond said rings, the portion of said cap terminating beyond said rings being provided with an internal bevel extending rearwardly and inwardly to the rear of one of said rings.

SAUL WEISS.

' nEFERENcEsVorrED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

